This invention relates to a two-way cooling pipe for supplying cooling water in a circulating manner to the inner part of a die or mold to cool the die or mold which is used for die casting or a plastic forming process. The two-way cooling pipe is a single cooling pipe which has a forward channel and a backward channel inside for the passage of cooling water. The cooling water goes into the inner part of the die through the forward channel and, after performing heat exchange within the die, flows out through the backward channel.
As shown in FIGS. 6 and 7, a conventional two-way cooling pipe includes a forward channel and a backward channel for the passage of the cooling water with a double tube construction. Such a construction includes an outer hollow pipe a and an inner hollow pipe b having a smaller concentrically inserted therein. The inner pipe b serves as the forward channel X and the clearance between the outer pipe a and the inner pipe b serves as the backward channel for the cooling water. In the fabrication of the conventional cooling pipe with such a construction, it is necessary to insert the inner pipe b in the outer pipe a in a concentric position and connect them together by welding, brazing or soldering to the water stopper c, and also connect the water intake nozzle d to the forward channel X and the water outlet nozzle e to the backward channel Y by welding, brazing or soldering. This involves a difficult technique of inserting the inner pipe in the outer pipe concentrically and welding, brazing or soldering both pipes together in the concentric position (i.e. the so-called alignment) and the water intake and outlet pipes d, e to the outer and inner pipes a, b. These difficulties result in high production costs and leakage problems and poor water circulation. Furthermore, owing to the double pipe construction, more material is needed, resulting in an increase in material costs. These factors have made the conventional cooling pipe a very expensive device.